It has become common to standardize chromatographic and fuel cell type breath alcohol measuring devices with a dry standard gas, particularly a gas of the type described in Hutson U.S. Pat. No. 3,847,551. However, this type of standardizing gas has not worked well with IR (infrared) detectors of the type commonly used heretofore. Such IR detectors are well known and will not be described in detail. See, for example, U.S. Pat. No. 4,363,635. In these conventional IR detectors, the cell walls were usually anodized aluminum, with a coating of aluminum oxide on them, or occasionally steel on which rust forms. These metal oxides characteristically adsorb water and alcohol. When the conventional standardizing mixture of humid air and alcohol is used, the water vapor is adsorbed, and the alcohol measured, so that, for a given temperature, reproducable results can be obtained under the proper conditions (but see the description in U.S. Pat. Nos. 3,847,551, and 4,278,636). With a dry carrier, I have discovered that the alcohol itself is adsorbed, leading to erratic results.
One of the objects of this invention is to provide a method of standardizing IR cells by which dry standardizing gas can be utilized.
Other objects will become apparent to those skilled in the art in the light of the following description and accompanying drawing.